Sponsorship and affidavit of support letters
A support letter is drafted by the sponsor, so the signature normally needs certification, and it must always be filed together with evidence of the sponsor's own financial capacity.
A support letter is the sponsor's statement that they will cover the traveller's or student's expenses for a defined period. It should state the relationship, the scope of expenses covered, the period and contact details, since the receiver may verify it.
Because it is a privately drafted document, destination authorities usually require the sponsor's signature to be certified. In Thailand that certification is the work of a Notarial Services Attorney licensed by the Lawyers Council of Thailand.
The letter alone proves nothing about capacity, so it must be accompanied by the sponsor's own evidence: a balance certificate, statements and proof of income. The receiver assesses the whole bundle together.
If the sponsor is abroad, check whether that country requires signing before a local notary public or before a Royal Thai Embassy officer, and what certification chain applies before the document is used in Thailand or forwarded to a third country.
Documents to prepare
- The signed support letter
- Proof of relationship such as house registration, birth certificate or marriage certificate
- The sponsor's balance certificate and bank statements
- Proof of the sponsor's income
- Passport or ID copies for both sponsor and beneficiary
Step order
- Draft the letter stating relationship, scope of expenses and period clearly
- Sign before a Notarial Services Attorney
- Assemble the sponsor's financial evidence as one bundle
- Translate and legalise at the Department of Consular Affairs where required
- Obtain destination-embassy endorsement where that country requires it
Pre-filing checklist
- The beneficiary's name matches the passport
- The period and scope of covered expenses are stated
- The sponsor's financial evidence is complete
- The sponsor's signature is certified as the receiver requires
- The sponsor's contact details actually work
Practical tips
- State the covered expenses specifically — tuition, accommodation, travel — rather than a blanket promise
- Have the sponsor sign in the same form as the signature in their passport
- Keep the sponsor's bundle separate from the traveller's so the officer can review each quickly
Common pitfalls
- An uncertified signature where the receiver required certification
- No sponsor financial evidence attached, leaving the promise unsupported
- A claimed relationship with no supporting record such as a house registration or birth certificate
Frequently asked questions
Does a support letter need a certified signature?
A support letter requires a certified signature depending on the receiving authority's rules. Because the sponsor drafts the letter privately, most foreign authorities require signature certification performed by a Thai lawyer authorized as a notarial services attorney.
Must the sponsor be a relative?
Thai law sets no fixed rule, but receivers give weight to a provable relationship and a coherent reason for the support.
Must the sponsor's financial evidence be attached?
The sponsor's financial evidence must be attached to the support letter because the letter alone does not prove financial capacity. Receiving authorities assess the supporting documents as a complete bundle, evaluating both the formal letter and the accompanying bank records together.
What if the sponsor is overseas?
Check whether that country requires signing before a local notary public or before a Royal Thai Embassy officer, then complete that country's legalisation sequence before use.
Does the letter expire?
The receiver sets the validity it accepts. Issue the letter close to the filing date and state a support period covering the stay applied for.
For a document review before you file, contact us on LINE @nycli, call +66-83-249-4999 or email nycli@ilc.ltd. Our team will confirm the steps, any missing documents and a realistic timeline for your case.
Related cases
- Bank statements for use abroad
- Bank balance certificates
- Salary certificates and proof of income
- Loan, mortgage and liability documents
- Cross-border transfers and source-of-funds evidence
Official references
Requirements on this page follow the rules published by the authorities below. Always confirm the latest notice on the official site before filing.
- Bank of Thailand
- Securities and Exchange Commission (SEC)
- Department of Consular Affairs, MFA ThailandThailand's authority for document legalization and Apostille
- HCCH — Apostille Section (Hague Convention 1961)Thailand's accession enters into force 28 February 2027
Related services
Fees depend on document type, number of pages and turnaround. Send scans to LINE @nycli, call +66-83-249-4999 or email nycli@ilc.ltd for a written quotation.