@Rob ********
be careful... this advice is not accurate for every country. Some countries require citizens to pay taxes in their home country no matter where their residence is.
For example - US citizens pay federal income tax on global income no matter where they live. There are some exceptions, ways to avoid, and loop holes but this is the basic level for average citizens. If someone works for a US company then federal taxes will be withheld. If a US citizen works for a foreign company they are required to report foreign income as well.
Thailand is looking to implement new tax laws that tax income of foreigners staying longer than 180 days in a calendar year but the details aren't finalized on what income will be included, how to calculate, etc. Either way, Thailand and USA have a tax treaty that allows taxes paid to USA to offset the income taxes here. So if the Thai tax rate is higher then would sill likely need to pay, if Thai tax rate is lower then no payments but still need to file.
But once again, the details of the tax changes have not been finalized. It's kinda crazy that they might implement something that is based on previous year rather than future years.