Just go to your local immigration office and wait in line…avoid going there 1200 (noon) it’s closed for lunch break…the earlier the better it anytime after noon is good as well they always stay open after closing hours for the visa seekers…
Yes as soon as you land if it’s within the working hours of immigration you can go and apply for a 30 day extension…Cost is ฿1,900 baht and bring passport pics with you, the paperwork you can fill out there
Nothing is ever 100% certain but usually there is no problems as long as you didn’t do anything to get the red stamp in your passport prior to departure from Thailand…
No problems as long as you have the 60 day SETV in your passport already…but if you feel worried just go online and buy a LCC (low cost carrier) ticket to a close location (Malaysia, Singapore, Vietnam etc)