I run a small IT business in Bangkok without having a workpermit. I also employed an Indian developer for nearly a year, without workpermit. This developer has resigned from the company. Should I worry about any negative actions he could undertake against my company, having employed illegal alien?

YES!

Of course yes. You have to be very much worried if the guy left in bad terms with you and if you have given his any employment letter or any salary slip under the Company Name.

As far as I can see, you have done several illegal activities here;

1.You have engaged in business without any work permit.

2.You have employed an alien without a work permit.

3.You have not paid any taxes legally for running the business.

If you are very confident [90%] that this former employee will go and complain to any Thai Authority about your business etc, you can also black mail your former employee before he take any action against you.

He also has done several illegal activities here:

1.Most probably his stay in Thailand is illegal if he has worked for a Company under a tourist Visa. [ As far as I am aware, even seeking a job with a Tourist Visa is a punishable offence]

2.He can not engage in any Work without a work permit, where he has done.

3.He should file his personal tax returns, where he has not done.

If I were you, I will talk to the guy with above points and explain him the implications that he will have to face with if he proceed to take any action against you.

I am sure both of you will get Blacklisted and also will be deported from Thailand if this gets into any responsible Thai Department.

Above solution will not give you a 100% assurance. But I can not think of anything other than this.

Since both of you are part of this mess, it is only you two together can solve this.

Good Luck