Background: Children with delayed speech and language development are at considerable risk for later language impairment, social and behavioural problems, and illiteracy. Early diagnosis is needed for intervention planning and prevention. However, a speech and language test for Thai children has not been available. Aims: To establish a Thai Speech and Language Test for Thai children between zero and 2 years of age. Methods & Procedures: The authors reviewed both Thai and international speech and language development tests and studies related to factors associated with speech and language development. A Thai Speech and Language Test for children between zero and 2 years of age (TSLT2) was then formulated. The test was used with 419 typically developing Thai children in Khon Kaen, north-east Thailand. Outcome & Results: Language quotients were calculated to quantify/qualify Thai language development norms. Inter-rater reliability of the test ranged between 0.64 and 1, while internal consistencies ranged between 0.83 and 0.95 for tests on children between 1 and 2 years of age. Conclusions: Professionals or paraprofessionals can use the Thai Speech and Language Test for children between 1 and 2 years of age, which is the first Thai tool for the assessment, diagnosis and remediation planning of children with delayed speech and language development. It should be also adapted for use in other regions in Thailand. However, the test for children aged between 3 and 9 months should be revised and continue to be developed. (Contains 5 tables.)