Bro, sorry to burst your bubble but there are no such "guarantee of good conduct" documents for signing at immigration for normal entry pass, unless you are tokking about the sponsorship form which I am aware of is only applicable if u are extending the stay for the VB or applying for other types of passes/visa.
If you are toking about the personal guarantor letter, which I had already taught KT many years back, this method is already beaten to death by too many usage/abuses by all those VBs spreading this method around all these years. I remembered there was 1 superhero here in SBF that posted the whole template of that letter to "educate" the whole world, so in the end this method is already overused until ICA see until sian already
The visa-free 30 days is not a regulation, its simply a guideline for Asean countries and not all follows e.g. Myanmar. Even Sinkapor does not fixed this number of days and each case will be evaluated on its own merits, e.g. the VB that I sat with 2 weeks ago at W had only a 7 days entry pass, and she went to JB turn-around to renew the pass cos she tot can get 30 days this time round but again she kena 7 days entry pass again.
Each entry is always evaluated on its own merits depending on how ICA deems the person to be an "undesirable" or not, so entry into Sinkapor is not even guaranteed not to talk about the number of days, and they are not even obliged to provide you with the reason for refusing entry or restricting the number of days. There are many here that thought they can escort their VB through customs by travelling with them, but end up the VB got called into the ICA room and the escort are not even allowed to go in or even wait at the corridor, not to talk about giving them a chance to argue with the ICA on the regulations
Haiz......I think I may have said toooo much on this already

dun think too much on this okay, just a gentlemenly healthy debate on TCSS
Cheerios......SS08 ^_^