previous passport

Hi I am in serious trouble.

I live in Thailand.

my previous passport which has 5 years multiple visa and My employer kept my previous passport on the basis of which i gave resignation ..They accepted my resignation letter and hanged me for the passport that they will give this day that day and now they have refused to give me my passport and have issued the ticket and are forcefully asking me to leave the country .

What should i do ?

I want to know if i leave on my current passport will this weaken my case and will i loose my previous passport?

how will i be able to recover my previous passport by law ??

serious help needed.