Let’s Relax Onsen at Thonglor in Bangkok

Bangkok’s heat and traffic make a good case for an indoor retreat. At Let’s Relax Onsen and Spa Thonglor, you can trade the street for a Japanese-style bathing circuit, with several pools at different temperatures, a sauna, steam room, and cool-down spaces. It is an urban onsen, not a natural hot spring, but it offers a proper change of pace.

I like two things here: the variety of bathing facilities gives you more than one way to unwind, and the option to add a treatment lets you shape the visit around your time and budget. A day pass starts at US$21.55, while an onsen-and-massage package starts at US$40.15.

One thing to know before booking: the onsen zone is used without clothes, with only a small towel allowed. The spa is inside Centre Point Sukhumvit 55, not right beside the BTS, and the treatment you book must come after your soak.

The useful details at a glance

• Several pools, not just one hot bath: Expect pools at different temperatures, plus sauna, steam, warm Himalayan hot stonebed baths, and cool-down rooms.
• The day pass has no time limit, but allows one entry: You can stay as long as you like during that visit, but you cannot leave and return on the same pass.
• Choose your treatment before you arrive: Options range from 60-minute foot or back-and-shoulder massages to longer Thai massage and spa packages.
• Use the onsen before your treatment: Once your treatment begins, you cannot go back into the bathing area.
• The bathing rules are specific: No clothing or swimsuits in the onsen zone. A small towel is allowed there; wear the provided jinbei top and bottoms in the other facilities.
• Allow time to find the spa: It is at Centre Point Sukhumvit 55, at 300 Sukhumvit Soi 55, and some visitors have found the signs inside the hotel unclear.

A Japanese-style pause in Thonglor

Let’s Relax Onsen sits within the Centre Point Sukhumvit 55 hotel in Bangkok’s Thonglor district. The setting is urban and convenient if you are staying nearby, but the bathing area aims for a Japanese onsen feel, with wooden details, a quiet atmosphere, and a sequence of hot and cool spaces.

This is not a guided activity. You arrive at the spa, check in, and use the facilities or treatment included in your chosen package. Staff provide jinbei clothing for use outside the onsen zone. The bathing area itself follows Japanese-style rules: you bathe without clothes, and swimsuits are not allowed. If that is new to you, it is worth knowing before you arrive rather than discovering it at the changing area.

The main appeal is choice. You can keep the visit simple with a soak, or use it as the first part of a longer spa session. The facilities have been described as clean and well-kept, and the pools vary in temperature. That variety matters: you can move between warmer and cooler water, then take a break in the sauna, steam room, or cool-down area instead of spending your whole visit in one hot pool.

From check-in to the first pool

The visit begins at Let’s Relax Onsen and Spa Thonglor, inside the hotel. The spa is on the fifth floor according to visitors, and the route can be less obvious than the building address suggests. Follow hotel directions or ask staff once you arrive, and give yourself a little extra time rather than cutting it close to a treatment booking.

After check-in, you change and follow the facility’s clothing rules. The onsen area is for bathing without clothes, with a small towel as the only item you can bring in. Jinbei tops and bottoms are provided for the other facilities. This distinction is central to the experience, so it is a good fit if you are comfortable with a traditional communal bathing setup, and a poor fit if you expect to keep a swimsuit on.

The day pass includes unlimited time during one entry. In practice, that means you can take your time moving between pools and other facilities, but it does not mean you can leave for lunch and come back later. Several visitors describe five or more pools, and one mentions about seven facilities in the hot spring area. The exact number and availability can depend on what is open, so think of the place as a small bathing circuit rather than a fixed list of stations.

Pools, heat, and a proper cooldown

The pools are the heart of the visit. Different temperatures give you a reason to move around and find what feels comfortable, instead of treating the onsen as one long test of endurance. One useful approach is to alternate a soak with a rest in a cooler space, especially if you are not used to hot baths.

Beyond the pools, the included facilities are a sauna, steam room, warm Himalayan hot stonebed baths, and cool-down rooms. These make the day pass more substantial than a quick dip. You can use the heat in different ways, then step away to cool down before returning to a pool. One visitor specifically noted that an evening soak helped them sleep well afterward, though that is a personal outcome, not a promise.

Cleanliness and calm are frequent strengths of the experience. The bathing area is often described as clean, comfortable, and peaceful, with a Japanese-inspired design. Still, no spa is immune to maintenance needs. A visitor found the hot spring area under maintenance during a visit, and another reported a pest in the waiting area. Those appear to be exceptions in a generally positive picture, but they are worth keeping in mind if your plans depend on every facility being open.

Add a massage, scrub, or facial

If you book a treatment, use the onsen first. The spa does not allow you to return to the bathing area after treatment, so plan your visit in that order: bathe, cool down, then move on to your massage or other service.

The menu is broad. A 60-minute back-and-shoulder massage starts at US$22.30, a 60-minute foot massage at US$23.79, and a 120-minute Thai massage at US$35.69. Other options include aroma oil massage, hot herbal compress, four-hands Thai massage, body scrub, hot stone massage, and a 60-minute Dr. Spiller facial. Prices and package availability can change, so check the current options when you book.

Combined packages make sense if you want a full half-day reset rather than a short soak. Onsen plus a 60-minute Thai massage starts at US$40.15; the 120-minute Thai massage version starts at US$53.55. A combination of onsen, aromatherapy oil massage, and body scrub starts at US$92.19. The longer packages can run to 165 or 180 minutes, which is a considerable block of time but also bundles several services into one visit.

Massage quality is a strong point, though not perfectly uniform. Many people describe skilled therapists and pressure that feels well judged, while a few have found the technique too light or less impressive than expected. If you have a preference for firm or gentle pressure, say so before the session begins. That simple conversation may help you get more from the treatment.

What the price buys

The onsen day pass starts at US$21.55, while the experience summary gives a starting price of US$23.75. Treat these as indicative prices rather than a guaranteed checkout total, since rates can vary by package and booking date. For a Bangkok spa with pools, sauna, steam room, hot stonebed baths, and cool-down rooms, the pass offers decent value if you plan to use more than one facility and stay a while.

The better value may be a combined package if you already want a massage. For example, the onsen plus 60-minute Thai massage starts at US$40.15, only about US$18.60 more than the day-pass starting price. Compare the exact current rates before choosing, but a bundle can be a sensible way to turn a soak into a longer recovery session without paying separately for each part.

Small touches add to the experience. Some visits have included tea, snacks, pandan tea, wafers, or mango sticky rice after treatment. These extras are not guaranteed for every package or visit, so consider them a bonus rather than part of the price calculation.

Getting there and planning your visit

The address is Centre Point Sukhumvit 55, 300 Sukhumvit Soi 55, Sukhumvit Road, Khlong Tan Nuea, Watthana, Bangkok 10110. The location works especially well if you are staying at the hotel. It is not right by the BTS station, though some visitors have noted a hotel tuk-tuk shuttle to Thonglor BTS. Confirm local transport arrangements rather than assuming the shuttle will suit your timing.

Opening hours are listed as 10:00 to midnight every day. You need to make a reservation in advance for a treatment, ideally at least one day ahead, because preferred times can fill. The voucher itself is open-dated and valid for 180 days from confirmation, but it cannot be used on the purchase date.

Arrive on time. A late appointment may be shortened if you do not give notice, and it will be cancelled if you are more than 15 minutes late. If you are booking several tickets in one order, they arrive under a single voucher and QR code and must be redeemed together. Make separate bookings if you need to use tickets on different occasions.

The spa does not allow pregnant women or people with rashes or skin illness to use the service. Children aged 7 and older are allowed for treatment. If you need to cancel, the voucher can be refunded before it is used.

Who will enjoy this onsen

I would choose this for a slow afternoon or evening when you want an indoor break from Bangkok and would rather spend time bathing than rushing between sights. It suits couples, friends, solo visitors, and hotel guests who want an easy spa stop without arranging a trip outside the city. The day pass is particularly appealing if you enjoy trying different pool temperatures and using the sauna or steam room.

It is less suitable if you are uncomfortable with communal bathing without clothes, need to keep a swimsuit on, or want a natural hot spring in a rural setting. The location is also not the easiest option if your priority is stepping straight off the BTS and into the spa. And if you are booking a massage mainly for a particular pressure or technique, communicate your preferences clearly and keep expectations measured: the overall standard is often strong, but individual sessions can vary.

Should you book Let’s Relax Onsen Thonglor?

Book it if you want a clean, calm, Japanese-style bathing experience in the city, especially if you can pair the soak with a massage. The range of pools and heat facilities makes the day pass more worthwhile than a single quick dip, and the combination packages can be good value for a longer visit.

Skip it if the no-clothing rule is a deal-breaker, or if you need certainty that every facility will be open at your chosen time. Reserve treatments in advance, arrive early enough to find the fifth-floor spa, and soak before your treatment. Those three details will help the visit go smoothly.

FAQ

Where is Let’s Relax Onsen and Spa Thonglor?

It is at Centre Point Sukhumvit 55, 300 Sukhumvit Soi 55, Sukhumvit Road, Khlong Tan Nuea, Watthana, Bangkok 10110.

What are the opening hours?

The spa is listed as open daily from 10:00 to 00:00.

How much does the onsen day pass cost?

The day pass is listed from US$21.55. Prices may vary by package and booking date.

Does the day pass have a time limit?

It includes unlimited time during one entry. You cannot leave and return on the same pass.

Are swimsuits allowed in the onsen?

No. Clothing is not allowed in the onsen zone. You may bring a small towel, and jinbei tops and bottoms are provided for the other facilities.

What facilities are included with onsen access?

Onsen access includes the bathing area and access to facilities such as a sauna, steam room, warm Himalayan hot stonebed baths, and cool-down rooms.

Can I use the onsen after a massage or other treatment?

No. You must use the onsen before treatment, and you cannot return to the onsen afterward.

Do I need to reserve a treatment?

Yes. Make a reservation in advance for your preferred date and time. Booking at least one day ahead is recommended.

Are children allowed?

Children aged 7 and older are allowed for treatment.

Can I cancel and get a refund?

You can request a full refund before using the voucher.