@Ro**
, the big question is:
Where are you going to apply for the single entry tourist visa? In your country before you wing your way here OR from a thai consulate in a neighboring country?
That makes a LOT of difference on what documentation you will have to provide.
Right now the ONLY thai consulate in S/E Asia that doesn't require ANY of the 3-proof-ofz is the one in Vientiane.
FWIW: the 3-proof-ofz are:
proof of onward travel within 60 days
proof of 20K baht in a bank account
proof of a hotel booking or lodging