from openerp.tools.amount_to_text_en import amount_to_text

define a computed_field.

amount_to_text = fields.Char(string='Amount In Text', compute='convert')

define compute function.

@api.multi
def convert(self):
    """
    
    :param self: 
    :return: 
    """
    for record in self:
        currency_id = self.env.user.company_id.currency_id.id
        record.amount_to_text =  self._amount_to_text(record.amount,currency_id)

def _amount_to_text(amount, currency_id):
    # Currency complete name is not available in res.currency model
    # Exceptions done here (EUR, USD, BRL) cover 75% of cases
    # For other currencies, display the currency code
    currency = self.env['res.currency'].browse(currency_id)
    if currency.name.upper() == 'EUR':
        currency_name = 'Euro'
    elif currency.name.upper() == 'USD':
        currency_name = 'Dollars'
    elif currency.name.upper() == 'BRL':
        currency_name = 'reais'
    else:
        currency_name = currency.name
    #TODO : generic amount_to_text is not ready yet, otherwise language (and country) and currency can be passed
    #amount_in_word = amount_to_text(amount, context=context)
    return amount_to_text(amount, currency=currency_name)

you can do it In the studio add new field (char)
click on more > 
Compute > add these line of code 
for rec in self:
    currency = rec.currency_id.with_context(lang='YOU LANG CODE')
    amount_text = str(currency.amount_to_text(rec.amount_total))
    rec['x_studio_amount_in_word'] = amount_text

Hello,

get a free module: https://apps.odoo.com/apps/modules/12.0/jt_amount_in_words/