1. The only record the Irish authorities will have of your son being in Thailand will be his passport record which will contain a stamp showing entry and exit from Thailand during this 8 month period. Apart from this, there will be little record unless your son was convicted of an offence in Thailand in which case the Irish Consular authorities will have been notified of this fact and there will be a record in the Department of Foreign Affairs. However, I would advise your son to get a police certificate from Thailand if he can. It will at least show that he is being honest. Otherwise, he is likely to face problems if it emerges subsequently, such as when he is speaking with other course members or if the Gardai have some record of him being in Thailand.
2. Ultimately, honesty is the best policy if your son wants to work in the security industry. If he fails to disclose the fact of being in Thailand and it emerges subsequently, it will preclude your son from working in the industry. So, I would avoid this consequence.
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