An external beam PIXE (particle-induced x-ray emission) analysis was carried out according to the AGLAE (Accélérateur Grand Louvre d'Analyse Elémentaire) analytical system of the Laboratoire de Recherche des Musées de France, using a particle-induced accelerator to study a 14th-century thang-ka from the Musée Guimet collections in Paris. This work is part of a series of portable paintings linked to the local tradition of <i>sTag-lung</i>, a monastery founded in 1180 in central Tibet. Its striking effect is akin to that of illuminated manuscripts. The painting layer was first studied according to traditional methods, and PIXE analysis was employed to identify the mineral pigments and metal decorations found on this well-preserved thang-ka. The presence of an arsenic-based white pigment was revealed. The close examination of this painting also highlights the mastery of the artist in the preparation and use of the various available materials.