I will be flying to Thailand soon for 6 weeks, I'm I within the rules if I take a fortnight visiting Vietnam & Cambodia first, then spending my permitted 1 month in Thailand?
TLDR : Answer Summary
You can travel to Thailand for a total of 6 weeks, including 2 weeks in Vietnam and Cambodia before returning to Thailand for 30 days, as long as you are aware of the visa regulations. Upon arrival in Thailand, you will receive a 30-day stamp under the visa exemption program. However, if you plan to re-enter Thailand after your time in Vietnam and Cambodia, you need to check whether you will require a new visa or if the 30-day exemption is applicable again. Also, keep in mind that Vietnam and Cambodia may require separate visas for entry.