I refer to the definition of the legalization, as stated by article 2 of the The Hague Convention of 25th October 1961 (Apostille Convention) :
Article 2
[…].For the purposes of the present Convention, legalisation means only the formality by which the diplomatic or consular agents of the country in which
the document has to be produced certify the authenticity of the signature, the capacity in which the person signing the document has acted and, where appropriate, the identity of the seal or stamp which
it bears.
The Embassy of Belgium in Bangkok legalizes (official) documents intended for use in Belgium, in compliance with article 33 of the Consular Code and article 30 of the Code of Private International Law.
Mr. Degeye should first check with the Embassy of the Republic of Indonesia whether his signature can be legalized directly by the aforementioned Embassy, as the documents are intended for use in Indonesia (and not Belgium).
If this is not the case : I do not object legalizing the signature of Mr. Degeye. The consular fee amounts to THB 900 per signature to legalize.
However, my signature, or that of my colleague, Mr. Laurent Frederickx, will have to be legalized afterwards by the Legalization Division of the Ministry of Foreign Affairs of Thailand and the Embassy of Indonesia (since the documents are destined for use in Indonesia).