The Swiss man – identified as Jonathan Bold and Jonathan Clode in various media reports – is suspected of participating in a memorial to Maoist militant Thalikkulam Velekkad Sinoj, a senior leader of the communist People’s Liberation Guerrilla Army of the CPI, considered a terrorist organization by the Indian government.
Sinoj died last month when the bombs he was making accidentally exploded, according to Indian media.
The Swiss also attended a political meeting of the Communist Party of India (Marxist) to protest against bombings in Gaza, according to reports.
He was charged under the Foreigners Act with violating the conditions of his tourist visa which state that no foreigner can engage in political action in India, reports The Times of India.
"As per visa rules, a foreigner is forbidden from taking part in such meetings," senior district police official N. Vijaykumar was quoted as saying.
"Our officials are questioning him. At times, he speaks in French and in English and appears to be hiding information. We are seeking his remand and will produce him before a magistrate."
Times Now news channel's website showed footage of the bespectacled Swiss citizen, sitting on a makeshift bed and smiling at the camera at a police station in Thrissur district, about 280 kilometres (175 miles) from Kerala state capital Thiruvananthapuram.
Local police said they found Maoist literature in the luggage of the 24-year-old, who travelled to India with a woman companion on July 1st.
According to Swiss newspaper Le Matin, the arrested man is a trade union activist from Geneva.
Switzerland's Federal Department of Foreign Affairs (EDA) confirmed that a Swiss citizen had been arrested in India.
The EDA is in contact with Indian officials over the matter, spokesperson Pierre-Alain Eltschinger told Le Matin.
Indian media reports that the man will face a hearing on Wednesday.
The Maoist insurgency in India has cost thousands of lives. The rebels are believed to be present in at least 20 states but are most active in the states of Chhattisgarh, Orissa, Bihar, Jharkhand and Maharashtra.
The presence of foreigners in areas controlled by Maoists is a sensitive issue in India. A French group was accused of Maoist ties in 2012 in northeastern Bihar state, just a month after two Italian men were abducted by Maoist rebels in Orissa state.
They were both later released unharmed.
India's Maoist guerrillas, who claim to be fighting for the rights of poor tribal minorities and farmers, have waged a decades-long battle across central and eastern states to overthrow state and national authorities.
They often target police and government officials in deadly ambushes and mine attacks.