Demi Lovato‘s one-night-only Los Angeles show might not stay that way for long … ’cause TMZ has learned her team is actively exploring bigger venues and even a possible tour after overwhelming demand left thousands of fans in a frenzy.

Demi announced the L.A. show on her social media Monday morning, and sources with direct knowledge tell us over 200,000 people flooded the online queue for the October 25 concert at the Hollywood Palladium, which holds just 4,000 fans. Within 20 minutes, we’re told the show was sold out.

Our sources say Demi’s team immediately began discussing an expansion … looking at larger venues and mapping out logistics for a potential multi-city tour tied to her upcoming album, “It’s Not That Deep,” which drops October 24.

We’re told the show was meant to be a small, celebratory performance … a chance for Demi to reconnect with fans and debut songs from the new album, including her fan-demanded single “Kiss,” which dropped last Friday. But when ticket queues crashed and fans took to social media begging for more shows, the conversation quickly shifted from special event to possible tour strategy.

Our sources say the team is already reviewing options, however, nothing’s locked in yet. As one source put it bluntly … “When 200,000 people try to buy tickets to a 4,000 capacity show, you don’t ignore that kind of demand.”

Demi’s new era may have started as “It’s Not That Deep” … but judging by this response, it’s getting a whole lot bigger.

We reached out to Demi’s reps for comment … so far, no word back.