According to Osho, yes—another soul can enter a body when the host's inner resolve shrinks, leaving empty space. Weakness, fear, self-doubt and guilt contract the subtle body, inviting restless, pleasure-seeking spirits. Strong will and self-trust envelop and protect the body, even radiating a field that influences others. Cultivate resolve to prevent possession and expand consciousness.
If you feel weak and small inside, you leave room for pushy spirits; if you feel strong and trust yourself, you fill your space and nothing gets in.