MSP430FR4133

Example msp430fr413x_adc10_16.c demonstrates the internal temperature sensor:

https://dev.ti.com/tirex/explore/node?node=AL42JTImOOwWpUAlbx0W1w__IOGqZri__LATEST

The product page has links to one (or more?) thermostat reference designs.

https://www.ti.com/product/MSP430FR4133

So the on-chip temp sensor can only measure temperature of the MCU, if I want to measure external temperature, I can't use internal temp sensor?

The internal temperature sensor does measure inside the package, so it isn't ambient. I believe the value it reads is at a know-able offset from ambient. The harder part is if you want to measure outside your box (you haven't said).

I've always used an external temperature sensor. That thermostat reference design (TIDU516A) uses a thermistor, which I expect could be made to poke through your box. TI also makes a collection of temperature sensor ICs.