looks like a topic from yesterday, but please keep in mind to state your nationality and where you stay in Thailand. This would help us and others to advise you a bit better.
no, Savannakhet is still walk in, but documents should be addressed to Royal Thai Consulate Savannakhet/Laos, Attn: Consular Section. Yu can also go to Vientiane, but please keep in mind to book well in advance on there online appointment system.
while this is thai visa advise I sometimes surprised by the pure naitivity of OP. This request left me wonder a bit. The process is easy. You choose a school. The school will tell what they need from you. Usually just passport, copied all pages, 7 pictres, in case you had previously Non Ed already, they need transcripts from that school. In some cases, example you want to study Chinese they need your educational background from your home country. Hence I not sure how much more info you need. Only your chosen school can assist. BTW I leave the topic open....
now it's my turn to create the shitstorm. I deleted one member for labeling Thailand in a negative way. And I close comments. Neither we nor anyone can predict the outcome when you face IO with a lot of stamp, the IO make decision and he can refuse entry based on many reason (in most case no money as the reason). To avoid such situations get a proper Non Immigrant Visa which reflects your status in Thailand.