was planning on staying in bkk for 3- 4 months with a visit to cambodia at sum point prob later in the trip and poss a trip north to chiang mai.what would be the simplest way to go?can i get a visa exempt 30 day then to cambodia for a week and back to another 30 day exempt and then extend in bkk 30 day? for 3mnth.im 35 from uk.cheers