This site explains detail the eviction process in Texas. Here is the section of the Texas code governing evictions and forcible entry. In Texas, forcible entry without resort to judicial process is illegal. In other words, no self-help.
Sec. 24.001. FORCIBLE ENTRY AND DETAINER. (a) A person commits a forcible entry and detainer if the person enters the real property of another without legal authority or by force and refuses to surrender possession on demand. (b) For the purposes of this chapter, a forcible entry is: (1) an entry without the consent of the person in actual possession of the property; (2) an entry without the consent of a tenant at will or by sufferance; or (3) an entry without the consent of a person who acquired possession by forcible entry.
Here is the process governing evictions:
Sec. 24.005. NOTICE TO VACATE PRIOR TO FILING EVICTION SUIT. (a) If the occupant is a tenant under a written lease or oral rental agreement, the landlord must give a tenant who defaults or holds over beyond the end of the rental term or renewal period at least three days’ written notice to vacate the premises before the landlord files a forcible detainer suit, unless the parties have contracted for a shorter or longer notice period in a written lease or agreement. A landlord who files a forcible detainer suit on grounds that the tenant is holding over beyond the end of the rental term or renewal period must also comply with the tenancy termination requirements of Section 91.001. … (d) In all situations in which the entry by the occupant was a forcible entry under Section 24.001, the person entitled to possession must give the occupant oral or written notice to vacate before the landlord files a forcible entry and detainer suit. The notice to vacate under this subsection may be to vacate immediately or by a specified deadline. (e) If the lease or applicable law requires the landlord to give a tenant an opportunity to respond to a notice of proposed eviction, a notice to vacate may not be given until the period provided for the tenant to respond to the eviction notice has expired. (f) The notice to vacate shall be given in person or by mail at the premises in question. Notice in person may be by personal delivery to the tenant or any person residing at the premises who is 16 years of age or older or personal delivery to the premises and affixing the notice to the inside of the main entry door. Notice by mail may be by regular mail, by registered mail, or by certified mail, return receipt requested, to the premises in question. If the dwelling has no mailbox and has a keyless bolting device, alarm system, or dangerous animal that prevents the landlord from entering the premises to leave the notice to vacate on the inside of the main entry door, the landlord may securely affix the notice on the outside of the main entry door. (g) The notice period is calculated from the day on which the notice is delivered. (h) A notice to vacate shall be considered a demand for possession for purposes of Subsection (b) of Section 24.002. (i) If before the notice to vacate is given as required by this section the landlord has given a written notice or reminder to the tenant that rent is due and unpaid, the landlord may include in the notice to vacate required by this section a demand that the tenant pay the delinquent rent or vacate the premises by the date and time stated in the notice.