Sean Murphy (PB 27/12) has corrected some of George Best’s mistakes but both seem to be oblivious to the fact that there is no passport control between the UK and the Republic. This means that a Thai under the Irish visa waiver could probably travel to the UK via Ireland without a visa. However, with heightened security, airlines would certainly want an ID and they might refuse to carry a Thai without a British visa. Shop around! Any Thai citizen following this route is strongly advised to get British consular advice.
It seems to me that saying Ireland is not giving anything away is irrelevant and unhelpful.