The Immigration Act B.E. 2522 (1979) provides that aliens without proper documentation (i.e. valid passport and visa) are prohibited from entering Thailand. Accordingly, many refugees and asylum seekers are subject to arrest, detention, and deportation. Common Charges under the Immigration Act are Illegal entry and Illegal stay (including overstay).
The Penalties of the law are imprisonment not exceeding 2 years, or fine up to 20,000 baht, or both. Detention at an Immigration Detention Center (IDC) while awaiting repatriation to
country of origin or third country .

If you have no passport or other legal document that is the illegal entry and if you have no valid visa, expired or revoked visa (e.g. overstay) that is illegal stay. Offenses under the Immigration Act considered as criminal charges, officials under the Immigration Act (i.e., the Immigration Police) are considered inquiry officials under the Criminal Procedure Code. Therefore, people arrested and charged with offenses under the Immigration Act will go through the criminal justice process. After being penalized, the court will order that the offender (i.e., the alien) cannot stay in Thailand . This will be the end of the criminal procedure. After the criminal procedure, the immigration police can take over the offender’s custody from the local police. The Immigration Police has a duty to deport people back to their country of origin if they are staying illegally . The immigration police shall assign an ‘appropriate place of stay’ for aliens before leaving Thailand.

Generally, the offender will be detained in an immigration detention center (IDC) to await for deportation back to their country of origin, or travel to another country (e.g. resettlement in a third country). The offender may enter into a bail agreement with the Immigration Police in order to live outside of the IDC. The offender may apply to the NSM at this stage to challenge the deportation order. The immigration police has a discretion to release people on bail. Two requirements for bail agreement are Thai guarantor and bail money: 50,000 baht. If a person is released on bail, they will be allowed to live in Thailand temporarily. However, every 15 days, you must go to the IDC and inform that you are in Thailand.