Greetings in Thailand are very easy. Thais use one single phrase in most situations:

Use this phrase to say Hi or Hello in Thai. It is also used for Goodbyes -- yes, the Thai language uses the same words for hello and good-bye.

Here is a short video on how to say it. You can also see the hand gesture to use for greetings, called "wai". You should repeat that gesture when you greet someone.

Sometimes you see the phrase สวัสดี written as "Sawasdee" in English, with an "s" in the middle. But the pronunciation of สวัสดี is "Sawadee", or "Sa-wad-dee". The letter "ส" at the beginning is pronounced "s", but in the middle it is pronounced "d". Long story short, say "Sa-wad-dee", not "Sawasdee". (If you want to learn to read that, we have a free course for that.)

Thais usually don't use different phrases for Good Morning / Good Day / Good Afternoon / Good Evening / Goodbye. They just use สวัสดี ค่ะ /ครับ .
This greeting might be the most helpful phrase for any foreigner in Thailand. You can use it in formal situations as well as in everyday life or on the phone. It is also appropriate when you get introduced to someone (you don't need to say "nice to meet you" in Thai. Just say สวัสดี ค่ะ /ครับ ). There are less formal greeting you can use with friends (see below), but if you are not sure, better be safe and use สวัสดี ค่ะ /ครับ

So what's this ค่ะ or ครับ at the end? These words are called polite particles. For most situations you can follow one simple rule:

Why should you use polite particles? Because these polite particles make your greeting sound friendly. There are also many other polite particles that you could use, but using ค่ะ or ครับ is always correct.

There are many less formal ways to say hi or hello in Thai. Here are the easiest.
For women: 

Similar for men:

Here you see a video of the different versions for women:

If you are walking, a typical Thai greeting is to ask ไป ไหน "where are you going?"  This is not really meant to check where you go, but more colloquial. It is ok to answer ไป กิน ข้าว "I'm going to eat something", or เดิน เล่น "just walking for fun", even if you are going somewhere else.

Other typical Thai greetings are กิน ข้าว รึยัง "have you eaten?" or เป็น ยังไง บ้าง "how is it going?"

If you want to learn Thai for free online, you can join our course anytime from anywhere. You will learn basics like how to say hello, order food, go shopping, … Our course is fun and highly interactive, like a game. Go and try it out.