Tex. Bus. & Com. Code § 112.006

An out-of-state business entity whose transaction of business in this state is limited to the performance of disaster- or emergency-related work during a disaster response period or an out-of-state employee whose only employment in this state is for the performance of disaster- or emergency-related work during a disaster response period is subject to a transaction tax or fee, including a motor fuels tax, sales or use tax, hotel occupancy tax, and the tax imposed on the rental of a motor vehicle, that is imposed in this state, unless the entity or employee is otherwise exempt from the tax or fee.