According to Notification of the MOPH (No. 223) B.E. 2544 (2001) Re: Flavouring Agents,  flavouring agents are substances used for flavour or taste of food and shall be classified into 3 types as follows:

1. A natural flavouring agent means an agent for enchanting taste flavour which is physically derived from plants or animals and normally used for human consumption.

2. An imitate/imitation of a natural flavouring agent means a flavouring agent derived from chemical extraction or synthesized flavouring agent in which the extracted substances or synthesized susbtance shall be of the same chemical properties as of the natural products normally used for human consumption and shall mean to include imitation of a natural flavouring agent which contains natural flavouring agent contents as well.

3. A synthesized flavouring agent means a flavouring agent which is not discovered in natural products normally used for human consumption and means to include a synthesized flavouring agent which contains a natural flavouring agent or imitation of a natural flavouring agent.

A flavouring agent should bear the standard label as stipulated in the notification.

Reference

Ministry of Public Health Thailand. (2011). Notification of the MOPH (No. 223) B.E. 2544 (2001) Re: Flavouring Agents.