"For a Visa Extension at Thai Immigration after the first 3 months, you generally need to bring:
Passport (Original + Copies of photo page, current visa, and arrival stamp)
TM.7 Application Form (with a recent 4x6 cm photo attached)
TM.30 Receipt / Proof of Notification
Extension Fee (1,9** THB)
Visa-specific Documents (e.g., School/ED visa documents, Work Permit/Company papers, or Non-O relative documents depending on your visa type)
To ensure all your specific visa extension documents are
complete and hassle-free, you can consult directly with this
@Shwe *****
Page for guidance."