1.I think because Thai government thought if they make a lot of export or import the goods ,So its might stimulate Thai economy too.That why Thai government force than pay only 3%
2.I think because they got only dividend from stock ,so it's far for they has to pay only 10% of revenue of dividend.
3.I think because they need to more their profit out of Thailand so it's has to 10% for profit more but also they has to pay CIT in Thailand too.I think it's bad for their company to move money.