To extend is simple. The only issue is if you havent come to Thailand yet you are likely to get stopped at airport check in and asked to show a flight out within 30 days. (You might get away with it but not likely). Id get a cheap flight ready to book say with air asia to kuala lumpur,about 40 quid just in case you need to book it at check in. Youll then have to right the 40 quid off. Not the end of the world
with Emirates ? It tends to ne airline dependant if they ask for a flight out of thailand. Have a cheap flight out lined up ready so you can book at check in if required
Ive been in Thailand for 16 years and have always looked for the cheapest way to exchange my own currency (pounds). After 14 years i realised i could save about 5-6% by bringing my own currency then exchanging it here. You save the 220thb ATM fee plus you get a better exchange rate than your own bank give you via thai atm (avoid tourist area exchange kiosk where rates will be poor) plus your bank also charge an international withdrawal fee. So if you spend 2000 euro a month in cash youll save perhaps 100-120 euro a month. Obvious downside youll be in charge of a big lump of cash which could get lost or stolen.