Can I apply for a 90-day Non-O visa at a different immigration office in Thailand and how do I handle extensions and re-entry permits?

𝟭. 𝗝𝗼𝗺𝘁𝗶𝗲𝗻 𝗿𝗲𝗾𝘂𝗶𝗿𝗲𝘀 𝘀𝗲𝗮𝘀𝗼𝗻𝗶𝗻𝗴 𝗼𝗳 𝟴𝟬𝟬,𝟬𝟬𝟬 𝗳𝗼𝗿 𝘁𝘄𝗼 𝗺𝗼𝗻𝘁𝗵𝘀.

You are correct Jomtien requires the 800K baht banked money to be seasoned for the initial 90 day Non-O visa application

𝗖𝗮𝗻 𝗜 𝗴𝗲𝘁 𝗶𝗻𝗶𝘁𝗶𝗮𝗹 𝟵𝟬 𝗱𝗮𝘆 𝘃𝗶𝘀𝗮 𝗮𝘁 𝗮𝗻𝗼𝘁𝗵𝗲𝗿 𝗜𝗢? 𝗜𝗳 𝘀𝗼 𝘄𝗵𝗲𝗿𝗲 𝗶𝘀 𝗰𝗹𝗼𝘀𝗲𝘀𝘁?

You need to LIVE in the area where you apply and you need to be there thru the 90 day Non-O visa process AND the year extension process <- you have to get the year at the same office where you get the 90 day Non-O issued.

𝟮. 𝗛𝗼𝘄 𝗲𝗮𝗿𝗹𝘆 𝗶𝗻 𝗺𝘆 𝟵𝟬 𝗱𝗮𝘆 𝘃𝗶𝘀𝗮 𝗰𝗮𝗻 𝗜 𝗮𝗽𝗽𝗹𝘆 𝗳𝗼𝗿 𝗲𝘅𝘁𝗲𝗻𝘀𝗶𝗼𝗻? You can apply for the year extension when you have 30 days or less at most immigration offices (Bangkok, Chiang Mai and a few others allow you to do it when you have 45 days or less)

𝗖𝗮𝗻 𝗜 𝗼𝗿𝗴𝗮𝗻𝗶𝘀𝗲 𝗮 𝗿𝗲𝗲𝗻𝘁𝗿𝘆 𝗽𝗲𝗿𝗺𝗶𝘁 𝗼𝗻 𝘁𝗵𝗲 𝟵𝟬 𝗱𝗮𝘆𝘀 𝘃𝗶𝘀𝗮 𝗮𝗻𝗱 𝘁𝗵𝗲𝗻 𝗿𝗲𝘁𝘂𝗿𝗻 𝗻𝗲𝘄 𝘆𝗲𝗮𝗿 𝗮𝗻𝗱 𝗮𝗽𝗽𝗹𝘆 𝗳𝗼𝗿 𝗲𝘅𝘁𝗲𝗻𝘀𝗶𝗼𝗻?

You can get a re-entry permit once the 90 day Non-O visa is issued BUT remember, it's only valid for that 90 days, so you'd have to get back by the expiration date so you could apply for the year extension.

𝗜𝗳 𝘀𝗼 𝗶𝘀 𝘁𝗵𝗲𝗿𝗲 𝗮𝗻𝘆 𝗺𝗶𝗻 𝗼𝗿 𝗺𝗮𝘅 𝘁𝗶𝗺𝗲 𝗜 𝗰𝗮𝗻 𝘀𝗽𝗲𝗻𝗱 𝗼𝘂𝘁 𝗼𝗳 𝗰𝗼𝘂𝗻𝘁𝗿𝘆?

Nope, just be here on or before the date the visa expires to apply for the extension

𝟯. 𝗖𝗮𝗻 𝗲𝘅𝘁𝗲𝗻𝘀𝗶𝗼𝗻 𝗯𝗲 𝗮𝗽𝗽𝗹𝗶𝗲𝗱 𝗳𝗼𝗿 𝗮𝘁 𝗝𝗼𝗺𝘁𝗶𝗲𝗻 𝗶𝗳 𝗶𝗻𝗶𝘁𝗶𝗮𝗹 𝟵𝟬 𝗱𝗮𝘆𝘀 𝗲𝗹𝘀𝗲𝘄𝗵𝗲𝗿𝗲?

Nope it cannot. I answered that earlier..

Good luck with it,

Why not come here like you plan get the bank account, get the money in then on your trip and while you're there get a 90 day Non-O visa.

Arrive get stamped in for 90 days then get the extension