The lottery is one of only two forms of legal gambling in Thailand and it draws in over 19 million people—that’s 28.6% of the country’s population. It takes place twice per month, on the 1st and 16th, and is administered by The Government Lottery Office (GLO). For many of the street vendors who sell lottery tickets—known as “Salak kin baeng” in Thai—it’s not just a fun flutter; it’s their livelihood. But since the military took power in May 2014, sales have fallen and their profits are dwindling.

There’s a reason that most Thais buy their lottery tickets from street venders: they can be more affordable than the official government-licensed sellers. But that doesn’t mean they don’t try to rip people off, either. While legally they’re only supposed to sell them for 80 baht, the street vendors will often push their prices up and keep the difference. Especially if they’re selling a popular or lucky number.

For those who don’t want to buy a whole ticket, there are also the smaller Tote rows, where you can win by matching three of the numbers. The prize for these tickets is much lower—10 baht per one—but it’s still higher than the cash prize for the larger numbers.

If you’re lucky enough to get a winning ticket, you can claim your money at the shop where you bought it or from GLO and provincial CGD offices. If you’re outside the capital, you can only claim at the local provincial CGD office. Winnings are taxed at 1%.

If you’re thinking about buying a ticket, make sure to read the fine print carefully. There are a few things to consider, such as the odds of winning and how long you can play for. The best way to win is to play for as long as possible and try to pick the numbers that have a high probability of winning.