  This White Paper summarises potential key science topics to be achieved with
Thai National Radio Telescope (TNRT). The commissioning phase has started in
mid 2022. The key science topics consist of "Pulsars and Fast Radio Bursts
(FRBs)", "Star Forming Regions (SFRs)", "Galaxy and Active Galactic Nuclei
(AGNs)", "Evolved Stars", "Radio Emission of Chemically Peculiar (CP) Stars",
and "Geodesy", covering a wide range of observing frequencies in
L/C/X/Ku/K/Q/W-bands (1-115 GHz). As a single-dish instrument, TNRT is a
perfect tool to explore time domain astronomy with its agile observing systems
and flexible operation. Due to its ideal geographical location, TNRT will
significantly enhance Very Long Baseline Interferometry (VLBI) arrays, such as
East Asian VLBI Network (EAVN), Australia Long Baseline Array (LBA), European
VLBI Network (EVN), in particular via providing a unique coverage of the sky
resulting in a better complete "uv" coverage, improving synthesized-beam and
imaging quality with reducing side-lobes. This document highlights key science
topics achievable with TNRT in single-dish mode and in collaboration with VLBI
arrays.
