1 without the appropriate visa your airline may refuse boarding ( for eg
*****
days for TH.)
2 without a ticket back ( in the system) nobody would know if you need a visa or not?and would probably insist on one especially Th
3 authorities worldwide are aware of the "fake ( real) " ticket sites so beware of them now
4 return flights amendable might be your option.
5 be aware Thailand in particular is enforcing more to stop basically non- tourists using tourist exemption stamps and extensions. You could be refused on any future border bounce nowadays.