Introduction:
Thailand National Quitline (TNQ) has provided reactive and proactive tobacco cessation counseling for Thai smokers since 2009. The TNQ service has been continuously developed from traditional telephone counseling to cessation service. Interventions delivered via text messaging (short message service, SMS) increase access to educational and support services that promote smoking cessation across diverse populations. In 2019, TNQ begin developing a 2-way Short Message Service (2-Way SMS) to Quit. The 2-way SMS is an interactive mobile text messaging service designed to motivate smokers to quit.

Objectives:
The purpose of this study was to develop a 2-way SMS to Quit for smokers calling TNQ, and protocol for sending 2-way SMS.

Methods:
This study was designed to develop and provide initial testing of the 2-way SMS protocol. The 28 experts who expertise in counseling/smoking cessation services and 3 current smokers were recruited to validate the text and protocol.

Results:
The messages that the researchers developed were derived from literature review, interview smokers, and experts, which consisted of 49 messages and 2 components, i.e. 1) messages for advice and encouragement to quit smoking in which the smoker can interact with the service provider (admin), and the service provider will send messages for 21 consecutive days with a total of 37 messages (34 messages for quitting smoking and 3 messages for clients respond to TNQ) and 2) relapse prevention SMS is a message of advice and encouragement to prevent a repeat smoking. Service providers will send messages after the smoker receive 2-way SMS monthly for 6 months, consisting of 12 messages (11 messages for suggestions and encouragement, and 1 message for clients respond to TNQ).

Conclusion(s):
Although the 2-way SMS to Quit system has been developed, the initial testing should be explored.