Hi, (Irish) land at shenzhen 17.25 and flight on to BKK at 00.30

The most important detail is that your both itineraries are eligible with 24 hour visa free transit and you do not need any kind of visa. Now, if you want to exit the airport and you obviously do, you will approach transit counter immediately upon your landing into Shenzhen. This is the first thing you will do. There you will present your flight tickets and for this reason you are advised to print out your flight tickets while you are still in Ireland. In reality, you will there apply for a temporary entry permit. This application is free of any charge and the procedure is short with a hope that there will not be too many other passengers willing to do the same... After your permit is granted you will cross the immigration and take a metro line number 11 to reach the city. This is very easy and straightforward.

During your first landing, you can apply for a temporary entry, but you should be aware that the airport officials usually grant a permit to those with 8 hour layover or longer, to those who have overnight layover and to those traveling with small children. So, your first layover is the border case... In any vase, if I were you, I would apply and at least walk around the city center for a couple of hours instead of staying at the airport for quite a long time.

During your second layover, you will do the same procedure, but this time you are advised to have a printout of your hotel booking confirmation. You will be practically certainly granted a temporary entry permit to be allowed to have a decent night rest. To summarize... You will be definitely allowed to leave airside during your second layover and probably during the first one... Just follow the suggestions presented here and have a nice journey.