I´m not sure if this trip if I can do this but I believe this is possible if  i go backpacking.

Is there a tailored holidays that do the 3 in a few days or is that ridiculous.  I´m finding Cambodia to Vietnam easy enough but nothing with Thailand so can someone suggest best way and times.

Failing that would bangkok to Singapor be more realistic. if so how would i do that and roung costs. hope i find someone who knows.
Thanks for all your help.
=)