Is there term for thermophilic-halophilic plants and if so, what is it?
Well, at least in other biological contexts, such organisms are often simply referred to as being thermohalophiles (or as being thermohalophilic).
Examples of the use of these words:
Bacteria:

Mavromatis, K., Ivanova, N., Anderson, I., Lykidis, A., Hooper, S.D., Sun, H., Kunin, V., Lapidus, A., Hugenholtz, P., Patel, B. and Kyrpides, N.C., 2009. Genome analysis of the anaerobic thermohalophilic bacterium Halothermothrix orenii. PLoS One, 4(1).

Denger, K., Warthmann, R., Ludwig, W. and Schink, B., 2002. Anaerophaga thermohalophila gen. nov., sp. nov., a moderately thermohalophilic, strictly anaerobic fermentative bacterium. International journal of systematic and evolutionary microbiology, 52(1), pp.173-178.

Pereira, M.M., Antunes, A.M., Nunes, O.C., da Costa, M.S. and Teixeira, M., 1994. A membrane‐bound HIPIP type center in the thermohalophile Rhodothermus marinus. FEBS letters, 352(3), pp.327-330.


Biochemistry:

Amoozegar, M.A., Salehghamari, E., Khajeh, K., Kabiri, M. and Naddaf, S., 2008. Production of an extracellular thermohalophilic lipase from a moderately halophilic bacterium, Salinivibrio sp. strain SA‐2. Journal of basic microbiology, 48(3), pp.160-167.

I'll note that I haven't found evidence of plants being referred to in this specific manner, but read the example papers below for use of the related phrases &quot;thermohalophyte vegetation&quot; and &quot;thermohalophytes&quot;, respectively:

Accogli, R., Nutricati, E., Famà, L., Medagli, P., Manno, D., De Bellis, L., Marchiori, S. and Colasante, M., 2008. Iris revoluta Colas., natural hybrid origin species: characterization and preservation problems. Plant Biosystems, 142(1), pp.162-165.

Vekhov, N.V., 1996. Thermal and freshwater springs of the Chukchi Peninsula: Unique subarctic ecosystems. Part ii. flora. Polar Geography, 20(3), pp.209-220.


Is this word-blending approach the best or most appropriate? Couldn't say, but there is certainly prior  precedence for combining the habit adjectives into &quot;thermohalo-&quot;.