When Mark Thomas premiered his new show, Bravo Figaro, at the Traverse Theatre as part of the 2012 Edinburgh Festival Fringe, it came as something of a surprise.

Not just because this gobbiest of left-wing stand-ups had seemingly body-swerved the grassroots venues he normally plays to do something more theatrically formal. The content of the piece too was something of a curve-ball.

Where Thomas' previous visit to Edinburgh had been with Extreme Rambling – Walking The Wall, an account of Thomas's journey to the Middle East to walk the entire length of the Israeli Separation Border, Bravo Figaro was an all too personal story of Thomas' relationship with his opera-loving father. The show was framed around Thomas's reaction to his father contracting the degenerative illness progressive supranuclear palsy. He persuaded the Royal Opera House company to perform in his parents bungalow in Bournemouth.

Bravo Figaro was funny, honest, moving and surprisingly unsentimental, and was duly awarded a Bank of Scotland Herald Angel award. With the presentation taking place at the Bank of Scotland HQ on the Mound in Edinburgh, Thomas himself observed that it was a rare appearance for him in a bank where he wasn't being thrown out for asking difficult questions.

For one night only, Thomas brings Bravo Figaro to Glasgow as part of this year's Glasgow International Comedy Festival. The same night, he will follow his performance at Oran Mor with Manifesto Warm Ups, a pre-cursor to his latest series of Manifesto on Radio 4, in which he riffs with the audience on setting radical new agendas. Previous make-believe policies have included banning anyone who supports ID cards from having curtains, and legislation making it illegal for politicians to knowingly lie, dubbed Archer's Law.

While the two shows are completely different, Thomas sees the personal and political elements of both as two sides of the same coin. It also stops him slipping into increasingly predictable routines, as he explains.

"I like to surprise audiences," he says. "It's fun to do that, because as a performer, and somebody who's creative, I don't just want to do the same old stuff. For me, the idea of becoming one of these comedians traipsing round the same old circuit, doing the same old material, with the chill wind of your career's decline nipping at your heels, that would be my idea of hell. But it's good to surprise people.

"It's like in the old days, doing stand-up at the Comedy Store, if you had a really beery audience, I'd talk about the Mexican debt crisis. Whereas, if there was a twee, middle-class audience in, I'd talk about fisting or something. I think I've changed how I think about things since then. I'm always fascinated by politics, but this idea that it's something that labels me is ever so slightly irksome. It's like whenever I hear myself labelled as a political comedian and activist. I think to be an activist, you have to be active, and I've had my feet up for the last year.

"I think there is politics in Bravo Figaro, anyway. It's about class, and it's about my dad's expectations, and what was expected of him. The idea of working class improvement is a beautiful thing, and used to go hand in hand with trade unionism, with this real emphasis on widening your sphere of knowledge. So the two things go together. It's like that George Orwell quote. Every laugh is a little revolution. I love that."

In truth, it's difficult to separate Thomas's life from his work, and this is something he has begun to exploit. "When I was doing Walking The Wall, during the interval, we'd have a Klezmer band come on and play some songs, then five minutes before the second half we'd show footage of the West Bank, so you'd see these things I'd been talking about in the first half, and you'd see the audiences faces thinking, Oh, God, that's true, and that's a fascinating thing. It's the same with Bravo Figaro. You hear my Dad's voice, and my brother's voice in the show, and there's this thing of trying to work out how you get all these other voices onstage that's kind of become an obsession."

Given the intimate nature of Bravo Figaro, what, one wonders, did Thomas's family make of it?

"My mum was really happy that the show was taking place," Thomas says. "She always felt the illness was under-reported. My dad was diagnosed fairly quickly, but early on it was still a struggle for us, so my mum was very keen that I should go out and talk about it, even though she doesn't feel she wants to see the show herself, because my dad's illness is something that's completely changed her life.

"My brother came to see it, mob-handed. It was like the whole of Essex came to the Royal Opera House. My sister and my nephew came, and they sat behind my tech operator. So my sister gets my nephew to sit on one side of her, gets a box of tissues out, and plonks it on her lap, ready to bawl. My Uncle came, and he's not very well, and afterwards he said: 'I tell you what, boy, I wish my boys would do something like that'. He thought, warts and all, it's about love, which it is."

As Thomas makes clear too, his family are no strangers to being used as material for his shows.

"They're kind of used to me doing stuff about them," he says, "and my sister's a vicar, so as you can imagine there's a lot of scope for material there. She was coming to see the show, and both my wife and my mum said to me, are you going to do all that stuff about her, and they basically talked me into not doing it. Then the day after the show, my sister rang me, and said, you didn't do any material about me. Why not?

"So you can't win. That's families for you."

Mark Thomas in Bravo Figaro and Manifesto Warm-Ups, Oran Mor, March 19 as part of Glasgow International Comedy Festival www.glasgowcomedyfestival.com