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A soi (ซอย) is a side street branching off a main road in Thailand. In a property listing it is the single most useful line of the address — the soi, and how far down it you are, decides your walk to the train, your noise at night, and most of your rent.
Thai addresses work outward from the front door. The road itself is the thanon (ถนน) — Sukhumvit, Silom, Sathorn. Branching off it are the sois, numbered lanes where nearly every home actually sits. Branching off those again are yaek, or sub-sois.
That structure is why the district on a listing tells you so little. Two condos in Watthana can be four minutes and forty minutes from the same office. The soi is what separates them.
Three things worth understanding before you read another listing.
A Thai address reads from the smallest unit outwards. Here is a typical one, taken apart:
123/45 Soi Sukhumvit 31, Khlong Toei Nuea, Watthana, Bangkok 10110
Sois are numbered outwards from where the main road begins, with odd numbers on one side and even numbers on the other. On Sukhumvit, odd sois run north and even sois run south.
Two homes on the same soi, at the same price per square metre, can be a completely different daily life. What separates them is how far down the lane they sit.
0–150 m from the main road · Under 2 minutes
150–600 m in · 2–8 minutes
600 m+, or down a yaek · 8+ minutes, or a motorbike taxi
Some sois are famous enough to have dropped the number. Listings use both forms, sometimes in the same sentence — these are the ones you will meet most often on Sukhumvit.
| Number | Known as | What it's like |
|---|---|---|
| Sukhumvit 3 / 4 | Nana Nuea / Nana Tai | North and south Nana. Dense, late-opening, walkable to Nana BTS. |
| Sukhumvit 21 | Asok Montri | The Asok–Phetchaburi axis. Offices, two train lines, heavy traffic. |
| Sukhumvit 23 | Prasanmit | Runs behind Asok. Quieter than the corner it starts from. |
| Sukhumvit 39 | Phrom Si | Long residential soi off Phrom Phong. Japanese schools and clinics. |
| Sukhumvit 49 | Soi Klang | Houses and low-rise condos, connects through to Thong Lo. |
| Sukhumvit 55 | Thong Lo | The one everyone means by “Thonglor”. Priciest end of the soi map. |
| Sukhumvit 63 | Ekkamai | Runs a long way north. The far end is a different market from the mouth. |
| Sukhumvit 71 | Pridi Banomyong | Residential, family-heavy, cheaper per sqm than 55 or 63. |
| Sukhumvit 77 | On Nut | Also called Soi On Nut. Long soi feeding a large residential belt. |
| Sukhumvit 101/1 | Punnawithi | A sub-soi that grew into a district of its own. |
Most people don't choose a soi in the abstract — they choose the school run or the station, and the soi follows. Start from whichever one matters to you.
Families pick the school first and the soi second. These campuses have homes listed within a 3 km radius today.
Stations with homes listed within an 800 m walk — roughly the length of a long soi.
A soi (ซอย) is a side street or lane running off a main road in Thailand. In a property listing, the soi is the part of the address that tells you the most: it sets your walk to the nearest BTS or MRT station, how quiet the property is at night, and usually the price. “Sukhumvit 31” means Soi 31 off Thanon Sukhumvit.
Not quite. A thanon (ถนน) is the main road; a soi is the lane that branches off it. Sois are typically one or two lanes wide, often dead-end, and can run for well over a kilometre. A yaek is a smaller lane branching off a soi again.
Sois are numbered outward from the point where the main road begins, with odd numbers on one side and even numbers on the other. On Sukhumvit, odd sois run north of the road and even sois run south. So Soi 31 and Soi 32 are not neighbours — they are across an eight-lane road from each other.
The slash marks a sub-soi, or yaek: 31/4 is the fourth lane branching off Soi 31. It also appears in house numbers, where 123/45 means unit 45 on plot 123. Both add walking distance that listings rarely mention.
Yes. Several Bangkok sois carry a name as well as a number, and listings use the two interchangeably. Thong Lo is Sukhumvit 55, Ekkamai is Sukhumvit 63, Asok is Sukhumvit 21 and On Nut is Sukhumvit 77.
Usually, yes — and the trade is walk time. Homes at the mouth of the soi command a premium for the short walk to transit and shops, while properties several hundred metres in are quieter and less expensive, but depend on a motorbike taxi or a car. Houses and gated estates are almost always further in, which is how they afford the space.
Now that the address makes sense, the practical half — which sois people actually rent in, what a soi position does to the rent, and what to check before you sign.