My dear sister is visiting in a couple months and will be doing other regional travels {Laos, Vietnam, Malaysia}. Will be traveling on a basic tourist visa (2 months). Do the Thai immigration authorities rquire an onward travel proof with this kind of visa? Thank in advance

No. Nor do the airlines.

As said a ticket is not needed.

But if she travels out of Thailand her tourist visa will be invalid for another entry unless she gets a visa with more than one entry or gets a re-entry permit at immigration.

If she was fly out and back for those trips she would get 30 days and by land only 15 days if she does not have a valid visa.

Edited August 26, 200917 yr by ubonjoe