First thing, we use different words for representing ourselves.
Girls, mainly, represent themselves as "Chan" or "Rao"
For guys are "Phom" or "Rao"(same as girls)
(But some girls use the word "Phom" just like guys and it's soo cuteee choose what you like!)
and if you want a polite sentence (same as "gozaimasu")
Girls usually end sentences with "Kah"(low tone) or "Kah"(high tone) depends on the situation.
And polite guys ALWAYS use "Krab" after finishing any sentence.
Okay, let's say the word "Hello" and "Hi" are
"Sawaddee" (Sawaddee Kah(low tone)or Krab to be more polite)